ggml-cpu : "align corners" for bilinear upscale/downscale (ggml/1285)

* add "align corners" mode for bilinear upscale, and allow downscaling
* add ggml_interpolate, deprecate ggml_upscale_ext, pass in align-corners as bit-flag
* test-backend-ops: replace ggml_upscale_ext with ggml_interpolate, add test cases for downscale and align-corners

Author: Acly

ggml/src/ggml.c

@@ -4465,6 +4465,7 @@ struct ggml_tensor * ggml_pool_2d_back(
 
 // ggml_upscale / ggml_interpolate
 
+static struct ggml_tensor * ggml_interpolate_impl(
 static struct ggml_tensor * ggml_interpolate_impl(
         struct ggml_context * ctx,
         struct ggml_tensor  * a,
@@ -4474,7 +4475,7 @@ static struct ggml_tensor * ggml_interpolate_impl(
         int64_t               ne3,
         uint32_t              mode) {
     GGML_ASSERT((mode & 0xFF) < GGML_SCALE_MODE_COUNT);
-
+    
     struct ggml_tensor * result = ggml_new_tensor_4d(ctx, a->type, ne0, ne1, ne2, ne3);
 
     ggml_set_op_params_i32(result, 0, (int32_t)mode);